Galvanic nickel or nickel alloy electroplating bath for depositing a semi-bright nickel or nickel alloy

ABSTRACT

The present invention is related to a galvanic nickel or nickel alloy electroplating bath for depositing a semi-bright nickel or nickel alloy coating characterized in that the electroplating bath comprises at least one compound having the general formula (I) 
     
       
         
         
             
             
         
       
         
         wherein R 1 =C 1 -C 18  hydrocarbon moiety substituted with a SO 3   −  group, C 1 -C 18  hydrocarbon moiety substituted with a carboxylic group or C 1 -C 18  hydrocarbon moiety substituted with at least an aromatic and/or a heteroaromatic group; 
         R 2 =NR 3 R 4  moiety, OR 5  moiety, or cyclic NR 6  moiety, wherein 
         R 3 , R 4 , R 5 =hydrogen or C 1 -C 18  hydrocarbon moiety or C 1 -C 18  hydrocarbon moiety substituted with at least an aromatic and/or a heteroaromatic group, wherein R 3 , R 4  and R 5  are identical or different; 
         R 6 =C 3 -C 8  hydrocarbon moiety or C 3 -C 8  hydrocarbon moiety, wherein at least one carbon atom is substituted by a heteroatom; and 
         n=1-3.

FIELD OF THE INVENTION

The present invention relates to a galvanic nickel or nickel alloyelectroplating bath for depositing a semi-bright nickel or nickel alloycoating on an electrically conductive work piece; and a methodtherefore. The invention is further generally directed to the use ofsuch a galvanic semi-bright nickel or nickel alloy electroplating bathfor depositing a bright nickel or nickel alloy coating by conducting themethod of the present invention. Additionally, the present inventionclaims absolute compound protection for the chemical compounds havingthe formulas (II), (III) and (IV).

BACKGROUND OF THE INVENTION

Bright nickel plating baths are used in the automotive, electrical,appliance, hardware and other industries. The most important functionsof bright nickel plating are as an undercoating for chromium plating,helping finishers achieve a smooth bright finish and providing asignificant amount of corrosion protection.

For decorative plated parts that need a high level of basis metalcorrosion protection, semi-bright nickel deposits are almost always usedin conjunction with subsequent deposits of bright nickel and chromium.The semi-bright nickel deposit is typically between about 60 and 70percent of the total nickel deposited on the part, which offers thehighest level of basis metal corrosion protection with the lowest totalnickel thickness and the best appearance.

The most common nickel plating bath is a sulfate bath known as a Wattsbath. In addition, in order to achieve bright and lustrous appearance ofthe nickel plating deposit, organic and inorganic agents (brighteners)are often added to the electrolyte. The types of added brighteners andtheir concentrations deter-mine the appearance of the nickel deposit,i.e., brilliant, bright, semi-bright, sat-in, etc.

Traditionally, coumarin has been used to obtain a high-leveling,ductile, semi-bright and sulfur-free nickel deposit from a Watts nickelbath. However, coumarin-free solutions are now available. A semi-brightnickel finish is semi-lustrous, as the name implies, but it wasspecifically developed for its ease of polishing and buffing. In thealternative, if subsequently bright nickel is plated, buffing can beeliminated. Brightness and smoothness are dependent on operatingconditions.

One of the reasons that semi-bright nickel finishes are so easily buffedand/or polished is that the structure of the deposit is columnar,whereas the structure of a bright nickel finish is plate-like(lamellar). However, the structure of the deposit can be changed withvarious additives, a change in pH, current density or an increase insolution agitation, which is not a problem unless it affects propertiesof the deposit such as internal stress.

Internal stress of the plated nickel deposit can be compressive ortensile. Compressive stress is where the deposit expands to relieve thestress. In contrast, tensile stress is where the deposit contracts.Highly compressed deposits can result in blisters, warping or cause thedeposit to separate from the substrate, while deposits with high tensilestress can also cause warping in addition to cracking and reduction infatigue strength.

The use of coumarin as an additive in nickel electroplating baths,especially semi-bright nickel processes, to produce ductile, lustrousdeposits with excellent leveling is well known. High concentrations ofcoumarin in the bath gives the best leveling results on one side, butsuch high coumarin concentrations also result on the other side in ahigh rate off formation of detrimental breakdown or degradationproducts. These degradation products are objectionable in that they cancause uneven, dull gray areas that are not easily brightened by asubsequent bright nickel deposit, they can reduce the leveling obtainedfrom a given concentration of coumarin in the plating bath, and they canreduce the beneficial physical properties of the nickel deposits.

The use of various additives, such as formaldehyde and chloral hydratehas also been suggested to help overcome the undesirable effects of thecoumarin degradation products. However, the use of such additives hascertain limitations because even moderate concentrations of thesematerials not only increase the tensile stress of the nickelelectrodeposits, but also significantly reduces the leveling action ofthe coumarin.

Even when since decades plating suppliers have proposed many bathformulations which claim to level as well as a coumarin bath, up to now,none of these baths formulations have met all of the necessary criteria.

As explained above, while the leveling of coumarin is exceptionalcoumarin has a disagreeable odor, breaks down and forms harmfuldegradation products, and these degradation products can only be removedby batch carbon treatments of the plating bath. These treatments areexpensive and time consuming and normally must be done at least monthlyand in some cases, even weekly.

DE 196 10 361 A1 discloses a process for a galvanic deposition ofsemi-bright nickel coatings on a substrate, wherein said substrate hasbeen treated by an acidic aqueous galvanic bath comprising a cyclicN-allyl- or N-vinyl-ammonium compound, in particular based onpyridinium, as brightener additive.

However, none of the known prior art suggests a way to achieve thedesired complex combination of good deposit properties of a semi-brightnickel or nickel alloy coating having good glance properties withoutgenerating high internal stress values. Prior art baths have solely beensuccessful to achieve semi-bright nickel or nickel alloy coatingsexhibiting some good properties while other properties have kept bad orturned bad, such a s combinations of good glance and high internalstress; or of bad glance and low internal stress.

Objective of the Present Invention

In view of the prior art, it was thus an object of the present inventionto provide an amended galvanic nickel or nickel alloy electroplatingbath for depositing a semi-bright nickel or nickel alloy coating on asubstrate, which shall not exhibit the aforementioned shortcomings ofthe known prior art nickel electroplating baths.

In particular, it was an object of the present invention to provide anamended galvanic nickel or nickel alloy electroplating bath which shallbe able for depositing a semi-bright nickel or nickel alloy coating on aplurality of different kind of substrates.

What is needed therefore is a way to deposit semi-bright nickel ornickel alloy coatings which possess good glance properties and a goodleveling.

It is another object of the present invention to provide a coumarin-freesemi-bright nickel or nickel alloy plating bath that approaches or evenequals the leveling characteristics of a coumarin bath.

Furthermore, it was an object to provide a semi-bright nickel or nickelalloy coatings which possess low internal stress, in particular incombination with good glance properties.

Additionally, it was especially an object of the present invention toprovide a semi-bright nickel or nickel alloy coatings which possesssolely a minimum of cracks and pores in order to avoid undesiredcorrosion of metal surfaces if the substrate to be coated comprisesmetal, e.g. steel.

It is still another object of the present invention to provide asemi-bright nickel or nickel alloy plating bath that provides goodstability over the life of the bath.

Further, it was an object of the present invention to provide an amendedgalvanic nickel or nickel alloy electroplating bath which shall be alsosuitable to be used for depositing bright nickel or nickel alloycoatings.

Further, it was an object of the present invention to provide an amendedgalvanic nickel or nickel alloy electroplating bath comprising a simpleas possible general bath composition, preferably with chemicals as cheapas possible.

SUMMARY OF THE INVENTION

These objects and also further objects which are not stated explicitlybut are immediately derivable or discernible from the connectionsdiscussed herein by way of introduction are achieved by a galvanic bathhaving all features of claim 1. Appropriate modifications of theinventive galvanic bath are protected in in dependent claims 2 to 12.Further, claim 13 comprises a method for depositing such a semi-brightnickel or nickel alloy coating on an electrically conductive work piece,while claim 14 comprises the use of such a galvanic semi-bright nickelor nickel alloy electroplating bath for depositing a bright nickel ornickel alloy coating by conducting such a method. Claim 15 comprisesabsolute chemical compound protection for the compounds having theformulas (II), (III), and (IV).

The present invention accordingly provides a galvanic nickel or nickelalloy electroplating bath for depositing a semi-bright nickel or nickelalloy coating characterized in that the electroplating bath comprises atleast one compound having the general formula (I)

wherein R₁=C₁-C₁₈ hydrocarbon moiety substituted with a SO₃ ⁻ group,C₁-C₁₈ hydrocarbon moiety substituted with a carboxylic group or C₁-C₁₈hydrocarbon moiety substituted with at least an aromatic and/or aheteroaromatic group;R₂=NR₃R₄ moiety, OR₅ moiety, or cyclic NR₆ moiety, whereinR₃, R₄, R₅=hydrogen or C₁-C₁₈ hydrocarbon moiety or C₁-C₁₈ hydrocarbonmoiety substituted with at least an aromatic and/or a heteroaromaticgroup, wherein R₃, R₄ and R₅ are identical or different;R₆=C₃-C₈ hydrocarbon moiety or C₃-C₈ hydrocarbon moiety, wherein atleast one carbon atom is substituted by a heteroatom; andn=1-3.

It is thus possible in an unforeseeable manner to provide an amendedgalvanic nickel or nickel alloy electroplating bath for depositing asemi-bright nickel or nickel alloy coating on a substrate, which doesnot exhibit the aforementioned shortcomings of the known prior artnickel electroplating baths.

In particular, the inventive amended galvanic nickel or nickel alloyelectroplating bath is suitable for depositing a semi-bright nickel ornickel alloy coating on a plurality of different kind of substrates.

The present invention provides a coumarin-free semi-bright nickel ornickel alloy plating bath that at least approaches the levelingcharacteristics of a coumarin bath.

The achieved semi-bright nickel or nickel alloy coatings possess goodglance properties and a good leveling.

Furthermore, the resulting semi-bright nickel or nickel alloy coatingspossess low internal stress, in particular in combination with goodglance properties.

Further, the present invention provides a semi-bright nickel or nickelalloy plating bath that provides good stability over the life of thebath.

Additionally, the obtained semi-bright nickel or nickel alloy coatingspossess solely a minimum of cracks and pores whereby any undesiredcorrosion of a metal surface can be successfully avoided if thesubstrate to be coated comprises metal, e.g. steel.

Further, the inventive amended galvanic nickel or nickel alloyelectroplating bath comprises a very simple general bath compositionwith mostly cheap single chemicals.

Brief Description of the Tables

Objects, features, and advantages of the present invention will alsobecome apparent upon reading the following description in conjunctionwith the tables, in which:

Table 1 exhibits experiments for semi-bright nickel coatings inaccordance with embodiments of the present invention.

Table 2 exhibits experiments for semi-bright nickel coatings inaccordance with comparative embodiments outside of the presentinvention.

Table 3 exhibits experiments for using semi-bright additives inaccordance with embodiments of the present invention for bright nickelcoatings.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “galvanic nickel or nickel alloy electroplatingbath”, when applied for depositing a semi-bright nickel or nickel alloycoating in accordance with the present invention, refers to a galvanicnickel bath, which is based on the so-called “Watts electrolytic bath”,which has the general following composition:

240-550 g/l nickel sulfate (NiSO₄•7H₂O or NiSO₄•6H₂O),  30-150 g/lnickel chloride (NiCl₂•6H₂O), and  30-55 g/l boric acid (H₃BO₃).

The large amount of nickel sulfate provides the necessary concentrationof nickel ions, while nickel chloride improves anode corrosion andincreases conductivity. Boric acid is used as a weak buffer to maintainthe pH value.

In the present invention, the galvanic nickel and nickel alloyelectroplating baths have chloride content ranging from 10 to 50 g/l,preferably ranging from 15 to 40 g/l, and more preferably ranging from20 to 30 g/l.

Nickel chloride may be replaced partly or entirely by sodium chloride.

Further, chloride in the electrolyte may be replaced partly or entirelyby equivalent amounts of bromide.

Furthermore, the galvanic nickel bath may comprise in certainembodiments of the present invention at least a wetting agent, such assodium salts of dihexyl sulfosuccinate, diamyl sulfosuccinate and/or2-ethylhexylsulfate, wherein the concentration of such a wetting agent,is used, is ranging from 5 to 500 mg/l, preferably ranging from 10 to350 mg/l, and more preferably ranging from 20 to 250 mg/l.

The cathodic current density amount to values ranging from 1 to 10A/dm², preferably ranging from 2 to 7 A/dm², and more preferably rangingfrom 3 to 5 A/dm².

The galvanic nickel or nickel alloy electroplating bath of the presentinvention can be deposited on a plurality of different kind ofsubstrates based on a metal and/or metal alloy, in particular steel,copper, brass and/or zinc diecasting; or on “POP” substrates. “POP”substrates mean in the sense of the invention plating on plastics. Thus,POP comprise a synthetic substrate, preferably based on at least onepolymeric compound, more preferably based onacrylonitrile-butadiene-styrene (ABS), polyamide, polypropylene orABS/PC (polycarbonate).

The expression n=1-3, 1 or 2, or 1 in general formula (I) of the presentinvention defines the number of substituents on the ring system ofgeneral formula (I). Thus, if n=3, the ring system of general formula(I) comprise three substituents, which can be arranged in ortho, metaand/or para position in relation to the nitrogen atom of the ring systemfollowing hereby the general known substitution rules of organicchemistry. Conclusively, if n=2, there are two of such substituents;while if n=1, there is solely one such substituent on the ring systempresent.

Electrolytes for obtaining matte nickel or nickel alloy deposits, bycontrast, do not form part of this invention.

In one embodiment, the electroplating bath further comprises an alkalimetal, preferably sodium, benzoate at a concentration ranging from 0.005to 5 g/l, preferably from 0.02 to 2 g/l, more preferably from 0.05 to0.5 g/l. Such additive compounds help to reduce internal stress of thedeposited coatings.

In one embodiment, the electroplating bath further comprises salicylicacid at a concentration ranging from 0.1 to 10 g/l, preferably from 0.3to 6 g/l, more preferably from 0.5 to 3.5 g/l. Such an additive affectspositively the hardness, durability and the optical properties of theachieved coatings.

In a preferred embodiment, the electroplating bath comprises at leastone compound having the general formula (I), wherein

R₁=C₁-C₈, preferably C₁-C₄, hydrocarbon moiety substituted with a SO₃ ⁺group, C₁-C₈, preferably C₁-C₄, hydrocarbon moiety substituted with acarboxylic group or C₁-C₈, preferably C₁-C₄, hydrocarbon moietysubstituted with at least an aromatic and/or a heteroaromatic group;R₂=NR₃R₄ moiety, OR₅ moiety, or cyclic NR₆ moiety, whereinR₃, R₄, R₅=hydrogen or C₁-C₁₈ hydrocarbon moiety or C₁-C₁₈ hydrocarbonmoiety substituted with at least an aromatic and/or a heteroaromaticgroup, wherein R₃, R₄ and R₅ are identical or different;R₆=C₄-C₈ hydrocarbon moiety or C₃-C₈ hydrocarbon moiety, wherein atleast one carbon atom is substituted by a heteroatom; andn=1 or 2.

In another preferred embodiment, the electroplating bath comprises atleast one compound having the general formula (I), wherein

R₁=C₁-C₈, preferably C₁-C₄, hydrocarbon moiety substituted with a SO₃ ⁻group, C₁-C₈, preferably C₁-C₄, hydrocarbon moiety substituted with acarboxylic group or C₁-C₈, preferably C₁-C₄, hydrocarbon moietysubstituted with at least an aromatic and/or a heteroaromatic group;R₂=NR₃R₄ moiety, OR₅ moiety, or cyclic NR₆ moiety, whereinR₃, R₄, R₅=hydrogen or C₁-C₈, preferably C₁-C₄, hydrocarbon moiety orC₁-C₈, preferably C₁-C₄, hydrocarbon moiety substituted with at least anaromatic and/or a heteroaromatic group, wherein R₃, R₄ and R₅ areidentical or different;R₆=C₄ or C₅ hydrocarbon moiety or C₄-C₅ hydrocarbon moiety, wherein atleast one carbon atom is substituted by a sulfur or oxygen atom; andn=1.

In a more preferred embodiment, the electroplating bath comprises atleast one compound having the general formula (I), wherein

R₁=n-ethyl-SO₃ ⁻, n-propyl-SO₃ ⁻, n-butyl-SO₃ ⁻, benzyl, CH₂—COOH or asalt thereof, preferably the sodium salt CH₂—COONa, moiety;R₂=NH₂, N(ethyl)₂, O(ethyl), OH moiety, or cyclic NR₆ moiety, whereinR₆=C₄ or C₅ hydrocarbon moiety or C₄-C₅ hydrocarbon moiety, wherein atleast one carbon atom is substituted by a sulfur or an oxygen atom; andn=1.

In one embodiment, the electroplating bath comprises at least onecompound having the general formula (I), wherein R₁ is not hydrogen.

In one embodiment, the working temperature ranges from 40° C. to 70° C.,preferably from 45° C. to 65° C., more preferably from 50° C. to 60° C.

In one embodiment, the electroplating bath comprises the at least onecompound having the general formula (I) at a concentration ranging from0.005 to 10 g/l, preferably from 0.008 to 5 g/l, more preferably from0.01 to 1 g/l.

In one embodiment, the at least one moiety C(O)R₂ is in ortho, metaand/or para position at the aromatic ring.

In one embodiment, the electroplating bath further comprises chloralhydrate at a concentration ranging from 0.005 to 5 g/l, preferably from0.02 to 2 g/l, more preferably from 0.05 to 0.5 g/l. Such an additivehelps to set up the potential and serves further to amend the glanceproperties and the throwing power of the deposited coatings.

In one embodiment, the electroplating bath further comprises at leastone compound selected from brighteners, leveling agents, internal stressreducers, and wetting agents, in particular at a concentration rangingfrom 0.005 to 5 g/l, preferably from 0.02 to 2 g/l, more preferably from0.05 to 0.5 g/l.

In one embodiment, the pH-Value of the electroplating bath ranges from 2to 6, preferably from 3 to 5, more preferably from 3.5 to 4.6.

In one embodiment, the electroplating bath comprises additionally atleast one bright nickel additive, preferably PPS and/or PPS-OH, whichis, if used without at least one compound having the general formula(I), unsuitable for depositing semi-bright nickel deposits. Theconcentration ratio between the at least one additional bright nickeladditive, such as PPS and/or PPS-OH, and the at least one compoundhaving the general formula (I) is less than 10:1, preferably less than5:1, and more preferably less than 3:1; wherein each of the at least onecompound having the general formula (I) and the at least one additionalbright nickel additive have a concentration ranging from 0.005 to 10g/l, preferably from 0.008 to 5 g/l, and more preferably from 0.01 to 1g/l.

This offers a tremendous advantage by being able to substitute largequantities of expensive compounds having formula (I) by cheap knownbright nickel additives, such as PPS and/or PPS-OH, without that theknown disadvantages of PPS and PPS-OH occur.

Further, the object of the present invention is also solved by a methodfor depositing a semi-bright nickel or nickel alloy coating on anelectrically conductive work piece, comprising the following methodsteps:

-   -   i) Bringing the work piece into contact with a semi-bright        nickel or nickel alloy electroplating bath according to the        present invention;    -   ii) Bringing at least one anode into contact with the        semi-bright nickel or nickel alloy electroplating bath;    -   iii) Applying a voltage across the work piece and the at least        one anode; and    -   iv) Electrodepositing a semi-bright nickel or nickel alloy        coating on the work piece.

Additionally, the object of the present invention is also solved bymaking use of such a galvanic semi-bright nickel or nickel alloyelectroplating bath for depositing a bright nickel or nickel alloycoating by conducting such a method, wherein additionally a primarybrightener is added to the semi-bright nickel or nickel alloyelectroplating bath.

Such a primary brightener can comprise unsaturated, in most casesaromatic sulfonic acids, sulfonamides, sulfimides,N-sulfonylcarboxamides, sulfinates, diarylsulfones or the salts thereof,in particular the sodium or potassium salts.

The most familiar compounds are for example m-benzenedisulfonic acid,benzoic acid sulfimide (saccharine), trisodium 1,3,6-naphthalenetrisulfonate, sodium benzene monosulfonate, dibenzene sulfonamide,sodium benzene monosulfinate, vinyl sulfonic acid, allyl sulfonic acid,sodium salt of allyl sulfonic acid, p-toluene sulfonic acid, p-toluenesulfonamide, sodium propargyl sulfonate, benzoic acid sulfimide,1,3,6-naphthalenetrisulfonic acid and benzoyl benzene sulfonamide.

Further, such a primary brightener can comprise propargyl alcohol and/orderivatives thereof.

The primary brighteners can be employed and added to the electrolytebath at a concentration ranging from 0.001 to 8 g/l, preferably from0.01 to 2 g/l, more preferably from 0.02 to 1 g/l. It is also possibleto use several primary brighteners simultaneously.

It has been surprisingly found in the context of the present invention,that new and inventive chemical compounds could be synthesized, whichhave been absolutely unknown up to now.

Further, the present invention claims absolute compound protection forthe chemical compounds having the following formulas (II), (III) and(IV):

In order to fulfill a sufficient disclosure of these absolute newchemical compounds, there will be given their synthesis procedures inthe following:

3-(3-(Diethylcarbamoyl)pyridinium-1-yl)propan-1-sulfonate (II)

10 g (0.0555 mol) of nicotinic acid diethylamide (99%) are dissolved in50 ml of ethanol. Subsequently 6.78 g (0.0555 mol) of 1,3-propanesultone are added. Then, the reaction mixture is cooked under reflux for48 hours at 78° C.After finishing of the reaction, the reaction mixture is cooled before100 ml of diethyl ether are added at room temperature. The resultingwhite solid is filtered at 4° C., washed with additional 100 ml ofdiethyl ether, and finally vacuum dried.9.00 g of a white solid is yielded (54% of theory).

3-(3-(pyrrolidin-1-carbonyl)pyridinium-1-yl) propane-1-sulfonate (III)

10 g (0.056747 mol) of 3-(pyrrolidin-1-carbonyl)pyridine are dissolvedin 50 ml of ethanol. Subsequently 6.93 g (0.056747 mol) of 1,3-propanesultone are added. Then, the reaction mixture is cooked under reflux for48 hours at 78° C.After finishing of the reaction, the reaction mixture is cooled before100 ml of diethyl ether are added at room temperature. The resultingwhite solid is filtered at 4° C., washed with additional 100 ml ofdiethyl ether, and finally vacuum dried.8.635 g of a white solid is yielded (51% of theory).

3-(3-(morpholin-4-carbonyl)pyridinium-1-yl) propane-1-sulfonate (IV)

10 g (0.05206 mol) of 3-(morpholine-1-carbonyl)pyridine are dissolved in50 ml of ethanol. Subsequently 6.36 g (0.05206 mol) of 1,3-propanesultone are added. Then, the reaction mixture is cooked under reflux for48 hours at 78° C.After finishing of the reaction, the reaction mixture is cooled before100 ml of diethyl ether are added at room temperature. The resultingwhite solid is filtered at 4° C., washed with additional 100 ml ofdiethyl ether, and finally vacuum dried.8.10 g of a white solid is yielded (49.5% of theory).

The present invention thus addresses the problem of providing an amendedgalvanic nickel or nickel alloy electroplating bath for depositing asemi-bright nickel or nickel alloy coating on a plurality of a differentkind of substrates. The inventive electrolytic bath offers a way toachieve semi-bright nickel or nickel alloy coatings having a good andunique combination of desired properties, such as glance, leveling,ductility and so on, whereas known prior art baths can solely providesome of these properties, wherein at least one severe disadvantage inform of a bad underside property is present. The inventive baths offerspar example on steel the desired property combination of having a goodleveling, a low hardness and a high ductility; and on POP's thecombination of a good glance and simultaneously low internal stressvalues.

The following non-limiting examples are provided to illustrate anembodiment of the present invention and to facilitate understanding ofthe invention, but are not intended to limit the scope of the invention,which is defined by the claims appended hereto.

In general, there has to be mentioned, that all experiments, comprisingthe experiments in accordance with the present invention as well as thecomparative embodiments outside of the present invention, has beenconducted using a so-called “Watts electrolytic bath” having thefollowing composition:

280 g/l nickel sulfate (NiSO₄•7H₂O),  35 g/l nickel chloride(NiCl₂•6H₂O),  35 g/l boric acid (H₃BO₃). and  50 mg/l sodium dihexylsulfosuccinate.

Further, at least one compound having the general formula (I) of thepresent invention was added to the above-cited basic Watts electrolyticbath.

The nickel deposition took place in a Hull cell wherein 2.5 Ampere wasapplied for 10 minutes at a temperature of 55° C.+/−3° C. Further, 3liter/min pressure air was introduced during nickel deposition.

The substrates have been pretreated in the following manner before theiruse for the nickel deposition:

-   -   i) Degreasing by hot soak cleaner    -   ii) Electrolytic degreasing    -   iii) Rinsing,    -   iv) Acid dipping with 10 vol % sulfuric acid

Sample substrates, made of copper and brass, have been scratched forsubjective optical judgment of leveling. The glance of the resultingnickel deposits on the substrates has been also judged optically.

All results shown in Tables 1, 2 and 3 for leveling, glance and internalstress are qualitatively ranked having the following synonyms:

+++ Excellent ++ Good + Medium − Bad

In case of internal stress excellent means very low stress or in idealcase no internal stress.

All concentrations given in Tables 1, 2 and 3 for the compound havingformula (I) as well as for the different further bath components arelisted in mg/l, if not stated differently. The basic electrolytic bathcomponents (Watts's bath) are listed above and will not be repeated inthe Tables, even if they are of course comprised. Golpanol BMP(2-butyne-1,4-diol propoxylate) is a commercially available brightener.

The experiments given in Tables 1, 2 and 3 are numbered in consequentorder wherein the second number in parentheses is an internal experimentnumber of the applicant.

The expression n=1 (meta) in the column “Additive” par example meansthat there is one substituent C(O)R₂ on the ring system, which ispositioned in meta position relating to the nitrogen atom of the ringsystem.

Turning now to the Tables, Table 1 shows conducted experiments forsemi-bright nickel coatings in accordance with embodiments of thepresent invention.

TABLE 1 Experiments for semi-bright nickel coatings Exp. Additive ConcBath Leveling Glance Stress  1 n = 1 (meta) 100 No further additives+++ + +++ (37) R₂ = N(Ethyl)₂ R₁ = (CH₂)₃SO₃ ⁻  2 n = 1 (meta) 100 75Chloral hydrate +++ ++ +++ (37) R₂ = N(Ethyl)₂ R₁ = (CH₂)₃SO₃ ⁻  3 n = 1(para) 100 75 Chloral hydrate +++ ++ +++ (38) R₂ = N(Ethyl)₂ R₁ =(CH₂)₃SO₃ ⁻  4 n = 1 (ortho) 100 75 Chloral hydrate +++ +++ ++ (39) R₂ =N(Ethyl)₂ R₁ = (CH₂)₃SO₃ ⁻  5 n = 1 (meta) 200 75 Chloral hydrate, +++++ +++ (54) R₂ = NH₂ 300 Na-benzoate R₁ = (CH₂)₃SO₃ ⁻  6 n = 1 (meta)200 75 Chloral hydrate, ++ + +++ (46) R₂ = OH 300 Na-benzoate R₁ =(CH₂)₃SO₃ ⁻  7 n = 1 (meta) 100 75 Chloral hydrate, ++ ++ +++ (27) R₂ =NH₂ 75 Golpanol, R₁ = CH₂COONa 200 Na-benzoate and Cl⁻  8 n = 1 (meta)200 75 Chloral hydrate, + + ++ (53) R₂ = OH 300 Na-benzoate R₁ =CH₂COONa and Cl⁻  9 n = 1 (meta) 20 75 Chloral hydrate ++ + ++ (34) R₂ =N(Ethyl)₂ R₁ = benzyl and Cl⁻ 10 n = 1 (meta) 200 75 Chloral hydrate,+++ ++ +++ (57) R₂ = N(Ethyl)₂ 300 Na-benzoate R₁ = (CH₂)₂SO₃Na and Br⁻11 n = 1 (meta) 200 75 Chloral hydrate, +++ ++ +++ (58) R₂ = N(Ethyl)₂300 Na-benzoate R₁ = (CH₂)₄SO₃ ⁻ 12 n = 1 (meta) 200 75 Chloralhydrate, + + ++ (59-1) R₂ = O-Ethyl 300 Na-benzoate R₁ = (CH₂)₃SO₃ ⁻ 13n = 1 (meta) 400 75 Chloral hydrate, +++ ++ ++ (59-2) R₂ = O-Ethyl 300Na-benzoate R₁ = (CH₂)₃SO₃ ⁻ 14 n = 1 (meta) 100 75 Chloral hydrate, +++++ ++ (37) R₂ = N(Ethyl)₂ 100 PPS, R₁ = (CH₂)₃SO₃ ⁻ 300 Na-benzoate 15 n= 1 (meta) 80 260 Chloral hydrate, ++ ++ ++ (37) R₂ = N(Ethyl)₂ 34butane R₁ = (CH₂)₃SO₃ ⁻ diol, 2500 salicylic acid, 140 hexindiol, 12Golpanol BMP 16 Formula (IV) 100 75 Chloral hydrate ++ ++ ++ (166)  [seeclaim 15] 17 Formula (III) 100 75 Chloral hydrate ++ ++ + (167)  [seeclaim 15]

Table 2 exhibits experiments for semi-bright nickel coatings inaccordance with comparative embodiments outside of the present inventionwherein known examples of the semi-bright nickel coatings have beenchosen, such as PPS and PPS-OH (experiments 19 and 20).

The comparative experiments exhibit often good results due to internalstress and leveling, but at the same time glance values are bad. Thisdiscrepancy is typical for known prior art systems in the semi-brightnickel coating industry as described before.

TABLE 2 Comparative experiments for semi-bright nickel coatings Exp.Additive Conc Bath Leveling Glance Stress 18 None — 260 Chloral hydrate,− − − 34 butane diol, 2500 salicylic acid, 140 hexindiol, 12 GolpanolBMP 19 No substituent 200 75 Chloral hydrate, + − +++ (55) PPS 300Na-benzoate R₁ = (CH₂)₃SO₃ ⁻ 20 No substituent 200 75 Chloral hydrate, +− ++ (56) PPS-OH 300 Na-benzoate R₁ = CH₂CH(OH) CH₂SO₃ ⁻ 21 Nosubstituent 100 75 Chloral hydrate ++ − − (18) R₁ = CH₂COOH and Cl⁻ 22No substituent 100 75 Chloral hydrate ++ − ++ (30) R₁ = CH₂CH(OH) CH₂OHand Cl⁻ 23 No substituent 100 75 Chloral hydrate + − ++ (31) R₁ =C₆H₆—COOH and Cl⁻ 24 N-allyl 100 75 Chloral hydrate − − − pyridiniumchloride DE19610361A1

A special surprising effect of a preferred embodiment of the presentinvention shall be outlined by a direct comparison of experiments 2, 14and 19, wherein in experiment 19 no inventive additive has been addedwhereas in experiments 2 and 14 the same inventive additive has beenadded, once without additional PPS (experiment 2) and once withadditional PPS in combination (experiment 14). But, the achieved nickelcoatings have similar qualities as can be easily seen above, even if PPSalone (experiment 19) is not suitable for achieving good semi-brightnickel coatings. This highlights the capabilities of the inventiveadditives having general formula (I) that they are not solely able togenerate good semi-bright nickel coatings, but also that they can bemixed and/or at least partially substituted by known cheap bright nickeladditives, such as PPS and/or PPS-OH, without losing their brilliantcoating qualities. This makes a possible commercial application evenmore promising. The same inventive effect is shown by comparingexperiments 15 and 18, wherein salicylic acid has been used as knownadditive for bright nickel baths.

Table 3 exhibits experiments for using inventive semi-bright additivesof the present invention for generating bright nickel coatings.

TABLE 3 Experiments for using semi-bright additives of the presentinvention for bright nickel coatings Exp. Additive Conc Bath LevelingGlance Stress 25 n = 1 (meta) 200 10 Propargyl alcohol +++ +++ +++ (37)R₂ = N(Ethyl)₂ 10 Na- R₁ = (CH₂)₃SO₃ ⁻ propargylsulfonate 800Na-allylsulfonate 4 g/l Na-saccharine 26 n = 1 (para) 200 10 Propargylalcohol +++ +++ +++ (38) R₂ = N(Ethyl)₂ 10 Na- R₁ = (CH₂)₃SO₃ ⁻propargylsulfonate 800 Na-allylsulfonate 4 g/l Na-saccharine 27 n = 1(ortho) 200 10 Propargyl alcohol +++ +++ +++ (39) R₂ = N(Ethyl)₂ 10 Na-R₁ = (CH₂)₃SO₃ ⁻ propargylsulfonate 800 Na-allylsulfonate 4 g/lNa-saccharine

Thus, the inventive additives can be also successfully used forgenerating bright nickel coatings by adding primary brighteners and/orby using other typical prior art bath components for bright nickelcoatings. The bright coatings of experiments 18, 19 and 20 exhibitedglance ranging from 0 (HCD) to 9.5 cm (LCD).

While the principles of the invention have been explained in relation tocertain particular embodiments, and are provided for purposes ofillustration, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims. The scope of the invention is limitedonly by the scope of the appended claims.

1. Galvanic nickel or nickel alloy electroplating bath for depositing asemi-bright nickel or nickel alloy coating characterized in that theelectroplating bath comprises at least one compound having the generalformula (I)

wherein R₁=C₁-C₁₈ hydrocarbon moiety substituted with a SO₃ ⁻ group,C₁-C₁₈ hydrocarbon moiety substituted with a carboxylic group or C₁-C₁₈hydrocarbon moiety substituted with at least an aromatic and/or aheteroaromatic group; R₂=NR₃R₄ moiety, OR₅ moiety, or cyclic NR₆ moiety,wherein R₃, R₄, R₅=hydrogen or C₁-C₁₈ hydrocarbon moiety or C₁-C₁₈hydrocarbon moiety substituted with at least an aromatic and/or aheteroaromatic group, wherein R₃, R₄ and R₅ are identical or different;R₆=C₃-C₈ hydrocarbon moiety or C₃-C₈ hydrocarbon moiety, wherein atleast one carbon atom is substituted by a heteroatom; and n=1-3. 2.Galvanic nickel or nickel alloy electroplating bath according to claim 1characterized in that the electroplating bath further comprises analkali metal, or ammonium benzoate at a concentration ranging from 0.005to 5 g/l.
 3. Galvanic nickel or nickel alloy electroplating bathaccording to claim 1 characterized in that the electroplating bathcomprises at least one compound having the general formula (I), whereinR₁=C₁-C₈, hydrocarbon moiety substituted with a SO₃ ⁻ group, C₁-C₈,hydrocarbon moiety substituted with a carboxylic group or C₁-C₈,hydrocarbon moiety substituted with at least an aromatic and/or aheteroaromatic group; R₂=NR₃R₄ moiety, OR₅ moiety, or cyclic NR₆ moiety,wherein R₃, R₄, R₅=hydrogen or C₁-C₁₈ hydrocarbon moiety or C₁-C₁₈hydrocarbon moiety substituted with at least an aromatic and/or aheteroaromatic group, wherein R₃, R₄ and R₅ are identical or different;R₆=C₄-C₈ hydrocarbon moiety or C₃-C₈ hydrocarbon moiety, wherein atleast one carbon atom is substituted by a heteroatom; and n=1 or
 2. 4.Galvanic nickel or nickel alloy electroplating bath according to claim 1characterized in that the electroplating bath comprises at least onecompound having the general formula (I), wherein R₁=C₁-C₈, hydrocarbonmoiety substituted with a SO₃ ⁻ group, C₁-C₈, hydrocarbon moietysubstituted with a carboxylic group or C₁-C₈, hydrocarbon moietysubstituted with at least an aromatic and/or a heteroaromatic group;R₂=NR₃R₄ moiety, OR₅ moiety, or cyclic NR₆ moiety, wherein R₃, R₄,R₅=hydrogen or C₁-C₈, hydrocarbon moiety or C₁-C₈, hydrocarbon moietysubstituted with at least an aromatic and/or a heteroaromatic group,wherein R₃, R₄ and R₅ are identical or different; R₆=C₄ or C₅hydrocarbon moiety or C₄-C₅ hydrocarbon moiety, wherein at least onecarbon atom is substituted by a sulfur or oxygen atom; and n=1. 5.Galvanic nickel or nickel alloy electroplating bath according to claim 1characterized in that the electroplating bath comprises at least onecompound having the general formula (I), wherein R₁=n-ethyl-SO₃ ⁻,n-propyl-SO₃ ⁻, n-butyl-SO₃ ⁻, benzyl, CH₂—COOH or a salt thereof,moiety; R₂=NH₂, N(ethyl)₂, O(ethyl), OH moiety, or cyclic NR₆ moiety,wherein R₆=C₄ or C₅ hydrocarbon moiety or C₄-C₅ hydrocarbon moiety,wherein at least one carbon atom is substituted by a sulfur or an oxygenatom; and n=1.
 6. Galvanic nickel or nickel alloy electroplating bathaccording to claim 1 characterized in that the electroplating bathcomprises at least one compound having the general formula (I), whereinR₁ is not hydrogen.
 7. Galvanic nickel or nickel alloy electroplatingbath according to claim 1 characterized in that the working temperatureranges from 40° C. to 70° C.; and/or that the pH-Value of theelectroplating bath ranges from 2 to
 6. 8. Galvanic nickel or nickelalloy electroplating bath according to claim 1 characterized in that theelectroplating bath comprises the at least one compound having thegeneral formula (I) at a concentration ranging from 0.005 to 10 g/l. 9.Galvanic nickel or nickel alloy electroplating bath according to claim 1characterized in that the at least one moiety C(O)R₂ is in ortho, metaand/or para position at the aromatic ring.
 10. Galvanic nickel or nickelalloy electroplating bath according to claim 1 characterized in that theelectroplating bath further comprises chloral hydrate at a concentrationranging from 0.005 to 5 g/l.
 11. Galvanic nickel or nickel alloyelectroplating bath according to claim 1 characterized in that theelectroplating bath further comprises at least one compound selectedfrom brighteners, leveling agents, internal stress reducers, and wettingagents, at a concentration ranging from 0.001 to 8 g/l.
 12. Galvanicnickel or nickel alloy electroplating bath according to claim 1characterized in that the electroplating bath comprises additionally atleast one bright nickel additive which is, if used without at least onecompound having the general formula (I), unsuitable for depositingsemi-bright nickel deposits.
 13. Method for depositing a semi-brightnickel or nickel alloy coating on an electrically conductive work piececomprising the following method steps: i) Bringing the work piece intocontact with a semi-bright nickel or nickel alloy electroplating bathaccording to claim 1; ii) Bringing at least one anode into contact withthe semi-bright nickel or nickel alloy electroplating bath; iii)Applying a voltage across the work piece and the at least one anode; andiv) Electrodepositing a semi-bright nickel or nickel alloy coating onthe work piece.
 14. A process for depositing a bright nickel or nickelalloy coating, comprising the following method steps: i) Bringing thework piece into contact with the semi-bright nickel or nickel alloyelectroplating bath according to claim 1, wherein additionally a primarybrightener is added to the semi-bright nickel or nickel alloyelectroplating bath; ii) Bringing at least one anode into contact withthe semi-bright nickel or nickel alloy electroplating bath; iii)Applying a voltage across the work piece and the at least one anode; andiv) Electrodepositing a bright nickel or nickel alloy coating on thework piece.
 15. A chemical compound having one of the following formulas(II), (III) and (IV):